Car is on last legs. Repair or purchase or both?

My 13 year old car is on her last legs. We have to put a new starter in this month, last month was tires and a battery. I have the opportunity to bid on a company fleet vehicle with low miles, and has been maintained regularly. Currently, there are no bids and the starting bid is less than $6k (about $5k below a clean retail). I'd have to pay to ship the car but if I stayed under retail, it would be a deal. Would you keep putting money into the old car, or put in a bid for the new one? Assume I have cash to pay for the new-to-me car.